Question: Solve for $a$ : $4 + a = 2$
Explanation: Subtract $4$ from both sides: $ \begin{eqnarray} \\ 4 + a &=& 2 \\ \\ {-4} && {-4} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{4 + a} &\hphantom{=}& \hphantom{2} \\ a &=& 2 {- 4} \\ \end{eqnarray} $ Simplify. $ a = -2$